1. Field of the Invention
The present invention relates to a lead wire connected to an output electrode provided on a magnetic transducer element of a magnetic head, more specifically, it relates to a two-layered tape lead wire which has a high flexibility, can be easily bent, can extremely reduce the bending spring rigidity and is suitable for a magnetic head having a reduced size and load, which is imposed by a head supporting device on the magnetic head, and lowered flying height and peripheral speed.
2. Discussion of Background
Conventionally, it is to constitute a lead wire connected to an output electrode provided on a magnetic transducer element of a magnetic head by a pair of twisted wires and to connect the tip of a loop to the output electrode of the magnetic transducer element, after the loop is formed by the pair of twisted wires. As described in the U.S. Pat. No. 4,928,195, for example, it is difficult for the lead wire consisting of a pair of twisted wires to cope with a reduction in size of a magnetic head, a reduction in a load imposed by a head supporting device on the magnetic head, lowering of a peripheral speed resulting from a reduction in length of the diameter of a magnetic disk, a lowering of the flying height, which is produced by a dynamic pressure generated between the magnetic disk and the magnetic head while the magnetic recording and reading are conducted, and furthermore, an increase in the number of output electrodes caused by an increase in the number of magnetic transducer elements. As the size of the magnetic head and the load imposed by a head supporting device on the magnetic head, and its flying height and the peripherial speed are more and more reduced, the magnetic head is likely to be affected by a spring rigidity of the loop portion of the pair of twisted wires, and exerts an adverse influence on the flying height, and the flying characteristics of the magnetic head.
To reduce the influence of the spring rigidity of the loop portion of the pair of:twisted wires on the flying height of the magnetic head, an attempt to reduce the diameter of the blank wires to about 30 .mu.m, for example, has been made, but this invites problems in that the bonding strength to the output electrodes drops and that the bonding to the output electrode becomes difficult with the reduction of the area of the output electrode due to the reduction in size of the magnetic head, because of the reduction in length of the diameter of the blank wires. Furthermore, in the case of a multiple device type of magnetic head, the bonding becomes extremely troublesome, because a large number of mutually independent blank wires exist in a small space.
Japanese Examined Patent Publication No. 59-31128, No. 60-12686 and No. 60-19045 disclose a technique using a flexible wire supporting a conductor film by a polymer resin film in place of the lead wire using lo a pair of twisted wires. FIG. 6 shows a flexible lead wire used in these prior art techniques, wherein reference numeral 1 is a polymer resin film, 2 is a bonding layer, 31 and 32 are conductor films, and 4 is a protective film. The conductor films 31 and 32 are bonded to the surface of the polymer resin film 1 by the bonding layer 2, and a laminate structure other than the protective film 4 constitutes a three-layered structure.
Nevertheless, the conventional prior art described above has the following problems.
(A) Since the structure is a three-layered structure in which the conductor films 31 and 32 are bonded to the surface of the polymer resin film 1 by the bonding layer 2, the total thickness and the bending spring rigidity are increased. The lead wire of the conventional three-layered structure has a thickness of 120 .mu.m or more, and it is practically difficult to obtain a thickness below this value. Therefore, when a structure is employed in which the tip portion of the flexible lead wire is bent and the conductor films 31 and 32 are bonded to the output electrodes provided on the magnetic transducer element of the magnetic head, the bending spring rigidity is imposed on the magnetic head by the flexible lead wire and exerts an adverse influence on the flying height and the flying characteristics thereof. As the size of the magnetic head and the load imposed on the magnetic head are reduced, and the flying height and the periphral speed are lowered, the magnetic head is more likely to be affected by the spring rigidity of the lead wire, and thus the flying height and flying characteristics of the magnetic head are deteriorated.
(B) When the flexible lead wire is used without bending, to avoid the adverse influence caused by the bending spring rigidity, the conductor films 31 and 32 and the output electrodes of the magnetic transducer element must be connected by other connection conductors to the flexible lead wire, and this deteriorates the operation of the assembly.
(C) As a means of reducing the bending spring rigidity, it may be possible to employ a structure which has a slit, formed by cutting partially the polymer resin film 1 at the portion corresponding to the bending portion. However, since the conventional flexible lead wire has the bonding layer 2, the bonding layer 2 swells out and leads to a problem such as an inferior bonding. Therefore, a structure which forms a slit and lowers the bending spring rigidity cannot be employed.